1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to the flattening of an interlayer insulating film that covers a capacitor in a DRAM.
2. Description of the Related Art
With the miniaturization of a DRAM (Dynamic Random Access Memory), sizes of all components become smaller. Even capacitors, which are important components of the DRAM, are no exception, and although the exclusive area of the DRAM tends to be reduced, the DRAM requires constant capacitance values in order to ensure the operation of a DRAM circuit. In order to earn the capacitance values, high-aspect-ratio capacitors having an increasing capacitor height, and particularly, crown type capacitors that use both outer and inner walls of cup-shaped capacitor lower electrodes have been used.
Since such high-aspect-ratio capacitors exist in a memory cell region on which storage cells are formed in the DRAM, the memory cell region has a height that is higher than that of a peripheral circuit region. Further, even in the peripheral circuit region, capacitors having the same shape as the capacitors formed in the memory cell region may be installed for the purpose of compensation capacitance and the like. An interlayer insulating film on a region on which capacitors are formed and on a region on which capacitors are not formed is formed to be higher than the capacitor, and is flattened by chemical mechanical polishing (CMP) for improvement of workability of wirings and the like thereon (JP2011-108927 A). In order to prevent the non -uniformity of flattening and to reduce a CMP load, the interlayer insulating film on a part of the capacitor is removed in advance by etching, and flattening is performed by the CMP (US2006/0284232 A).
US2006/0284232A discloses that a dummy pattern is put on the peripheral circuit region, and the interlayer insulating film on a region on which capacitors are formed is removed in part before the flattening. It has been revealed by a study by the present inventors that the interlayer insulating film on the region that remains through the etching causes the occurrence of cracks at the boundary between the region on which the capacitors are formed and the region on which the capacitors are not formed, and peels off through the CMP to cause a dent in part. A wiring material to be formed thereafter remains in the dent to cause a short-circuit problem.